1. Field of the Invention
This invention relates to a method of manufacturing a micro-lens array callable of condensing light at a high efficiency, as well as an electrolyte used therefore and an apparatus for manufacturing the micro-lens array.
2. Description of the Related Art
A method of manufacturing a micro-lens array includes a photo-lithographic process, an etching process such as dry etching, a method of doping a high refractive index material by thermal diffusion or a method of casting a plastic material into a previously formed mold thereby forming a micro-lens array. In the photolithographic process, any micro-lens array at high resolution power can be formed but the control for the curvature of lens is difficult. The dry etching method requires a long etching time and involves difficulty for the curvature control of lens. The method of doping the high refractive index material by thermal diffusion has an advantage of a material being a flat plate but undergoes various restrictions for the shape and the curvature of the lens since control is conducted only in view of the refractive index, and undergoes restriction for materials in that heat resistance is required and the method can be used only for glass substrates. The method of providing a previously formed mold involves a problem in view of the restriction for the micro miniaturization of the mold. Further, all the techniques mentioned above require high cost, and a technique for forming a micro-lens, which is simple and convenient and has a high degree of freedom, has not yet been available at present.
Further, as a low-cost method, there is a method of burying micro beads in a binder resin but it involves a problem that a uniform arrangement of micro beads is difficult.
The present inventors have previously provided an image forming method of excellent resolution and a manufacturing method of a color filter by use of an electrodeposition material containing a colorant and electro-precipitating or photo-electronically precipitating the material under the application of a low voltage, which are disclosed specifically, for example, in Japanese Published Unexamined Patent Application Nos. Hei 10-119414, Hei 11-189899, Hei 11-105418, Hei 11-174790, Hei 11-133224, and Hei 11-335894. The image forming method and the color filter manufacturing method described above have a feature of forming a colored film at a high resolution in a simple manner, but they are techniques applied mainly in the field of display devices such as liquid crystal display devices.
Further, the present inventors have proposed a photo-catalytic film deposition method of forming a colored film for a color filter or the like at a good resolution by a simple method like that the methods described above (Japanese Published Unexamined Patent Application No. Hei 2001-140096)
On the other hand, the micro-lens array is used for display devices such as liquid crystal projectors, as well as optical devices for condensing lenses. As described above, the micro-lens array has been prepared by fine fabrication of photosensitive materials by way of complicate steps including photolithographic method and an attempt of preparing a micro-lens array by an electrodeposition method without complicate steps such as photo-lithography has not yet been practiced at present.
This invention provides a method of manufacturing a micro-lens array capable of manufacturing a micro-lens array by a simple and convenient method at a reduced cost and capable of optionally adjusting a degree of integration and a refractive index of a micro-lens, as well as an electrolyte and a manufacturing apparatus therefor.
This invention provides the followings.
A method of manufacturing a micro-lens array including the steps of: disposing a substrate having a conductive thin film and a photo-semiconductor thin film in this order on an insulative base in an aqueous electrolyte containing a film-forming material of which solubility or dispersibility to an aqueous liquid is lowered by a change of pH, with at least the photo-semiconductor thin film of the micro-lens array preparing substrate being in contact with the electrolyte, irradiating with light a selected region of the photo-semiconductor thin film to apply a voltage between the photo-semiconductor thin film in the selected region and a counter electrode and precipitating the material to the selected region of the semiconductor thin film to form a micro-lens array layer.
This invention also provides the following.
A method of manufacturing a micro-lens array including the steps of disposing a substrate in which a conductive thin film and a photo-semiconductor thin film in contact with the conductive thin film are formed on an insulative base and the conductive thin film is in electrical conduction with an electrolyte to an aqueous electrolyte containing a film-forming material of which solubility or dispersibility to an aqueous liquid is lowered by a change of pH, with the photo-semiconductor thin film being in contact with the electrolyte, irradiating with light a selected region of the photo-semiconductor thin film in a state where the photo-conductive thin film is in electrical conduction with the electrolyte and precipitating the material to the selected region of the photo-semiconductor thin film to form a micro-lens array layer.